Technical Field
The present invention relates to the electrochemical field, particularly to an electrolyte solute and an electrolyte that are used for a high-voltage supercapacitor, and a high-voltage supercapacitor using the electrolyte.
Related Art
A supercapacitor, also referred to as gold capacitor or electrochemical capacitor, stores energy by means of ion adsorption (electric double layer capacitor) or a rapid surface redox reaction (pseudocapacitor). The supercapacitor is a novel energy storage device in between a cell and a conventional static capacitor. The number of charges stored by the supercapacitor is hundreds or thousands of times of that of a conventional electrolytic capacitor, and the supercapacitor can be completely charged or discharged within a few seconds, which has power input or output higher than that of a cell and can reach such power input or output in a shorter period of time. At the same time, the supercapacitor has the advantages of short charge and discharge time, long storage service life, high stability and wide operating temperature range (−40° C. to 70° C.), and has been widely applied in the field of consumer electronics products, the field of new energy generation systems, the field of distributed energy storage systems, the field of intelligent distributed grid systems, the transportation field such as new energy vehicles, the load field such as energy-saving elevators and cranes, the field of military equipment such as electromagnetic bombs, the motion control field, and the like, involving various sectors such as new energy generation, smart grid, new energy vehicles, energy-efficient buildings, industrial energy conservation and emissions reduction, and belongs to standard full range of low-carbon economy core products.
Compared with an electrochemical cell, the supercapacitor has a lower energy density and working voltage, and these disadvantages greatly limit the application of the supercapacitor in hybrid vehicles and electric vehicles. The energy storage formula of the supercapacitor is E=CV2/2, and therefore, the energy density of the supercapacitor can be effectively improved by increasing the working voltage of the supercapacitor. However, when working at a voltage exceeding 2.7 V, an electrolyte of a currently commercialized supercapacitor may be electrochemically decomposed, resulting in a significant increase in the pressure within the capacitor, and a significant decrease in the electrochemical performance, and finally resulting in a failure of the capacitor.
The working voltage of the capacitor is determined by the decomposition voltage of the electrolyte, and therefore, the bottleneck of the supercapacitor can be effectively broken through by developing an electrolyte used by a high-voltage supercapacitor, especially by finding a high-withstand voltage solute, and moreover, a good balance between a high withstand voltage and a long service life of the supercapacitor can further be achieved. Chinese Patent Publication No. CN100536048C discloses an electrolyte of a supercapacitor containing a mixture of N,N-dihaloalkyl-1,4-cis-1,4-bicyclic octanediium tetrafluoroborate and conventional tetraethyl ammonium tetrafluoroborate (Et4NBF4). The electrolyte of the supercapacitor has a certain high pressure resistance, but the service life characteristic of the supercapacitor is not described. Chinese Patent Publication No. CN101809693A sets forth that various acid scavengers are added to a conventional Et4NBF4 acetonitrile (AN) solution to alleviate an increasing rate of pressure in a capacitor, so as to achieve the purpose of improving a working voltage of the supercapacitor. This method can have a certain effect in the early period of using the supercapacitor, but with the extension of the service life, the electrochemical performance of the capacitor is significantly degraded, and the service life characteristic of the capacitor needs to be significantly improved.